Breathing apparatus

ABSTRACT

Breathing apparatus which incorporates a sensing device operable to adjust the amount of breather&#39;&#39;s exhaled gas captured in a gas collector section as a direct function of flow rate and volume of the previous inhalation. The amount of exhaled gas captured is sufficiently low in carbon dioxide (CO2) content to permit rebreathing on the next inhalation, at which time the sensor again adjusts the volume of exhaled gas to be captured. In the one embodiment, a fire fighter&#39;&#39;s breathing system is described wherein the gas collector section is integral with the breathing mask worn by the fire fighter.

United States Patent 11 1 Martin et a1.

[ 1 BREATHING APPARATUS [75] inventors: Frank E. Martin, Chester; JohnR.

Colston, Annapolis; Norman E. Smith, Pasadena, all of Md.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed. Nov. 6, 1973 [21] Appl. No.: 413,413

[52] U.S. C1. 128/142.2 [51] int. Cl.- A62B 7/04 [58] Fieid of Search128/1422, 142.3, 142, 128/1456,145.8,146.5,202,188,203,197, 196, 2.07,DIG. 17, 145.5; 73/27 R [56] References Cited UNITED STATES PATENTS2,633,843 4/1953 Glasser 73/27 R 2,743,167 4/1956 Cherry 1. 73/27 R3,021,839 2/1962 Marsh 128/202 3,266,869 8/1966 Dengler 1 1 4 128/2073,309,684 3/1967 Kahn et al. 1 1 128/207 3,358,681 12/1967 Chabanier128/1422 1 1 Oct. 21, 1975 3,396,723 8/1968 Freytag 128/145.6 35235278/1970 128/1458 3,548,821 12/1970 (jigauri 128/145.6 3557725 1/1971McQueen 128/188 3,680,556 11/1972 Morgan 128/1422 PrimaryExaminer-Richard A, Gaudet Assistant ExaminerHenry J. Recla Attorney,Agent. or Firm-D. Schron [57] ABSTRACT Breathing apparatus whichincorporates a sensing device operable to adjust the amount of breathersexhaled gas captured in a gas collector section as a direct function ofHow rate and volume of the previous inhalation. The amount of exhaledgas captured is suf ficiently low in carbon dioxide (CO content topermit rebreathing on the next inhalation, at which time the sensoragain adjusts the volume of exhaled gas to be captured. in the oneembodiment, a fire fighter's breathing system is described wherein thegas collec tor section is integral with the breathing mask worn by thefire fighter.

13 Claims, 10 Drawing Figures U.S. Patent Oct. 21, 1975 Sheet 2 ms3,913,576

I7 VOL LIMIT TO/FROM USER SENSOR F IG.3A

BREATHING GAS EXH

BREATHING GAS US. Patent 0a. 21, 1975 Sheet 3 of5 3,913,576

U.S. Patent Oct. 21, 1975 Sheet 4 of5 3,913,576

TIME

US Patent Oct. 21, 1975 Sheet 5 of5 3,913,576

BREATHING APPARATUS BACKGROUND OF THE INVENTION 1. Field of theInvention:

Breathing apparatusof the type wherein the user rebreathes a portion ofhis previously exhaled breath.

2. Description of the Prior Art:

Attempts have been made in the past to conserve the amount of breathinggas consumed from a breathing apparatus by allowing collectiotn andsubsequent rebreathing of the initial portion of exhaled gas.

This initial portion is low in carbon dioxide content and is referred toas the dead space or dead volume. Such breathing apparatus findswidespread use in the fields of diving, space, rescue work and ingeneral, instances where the user must be supplied with breathable gaswhile in a hostile ambient environment.

Previous systems relied on a technique for capturing a fixed volume ofexhaled gas within a distensible bag, the fixed volume being determinedby maximum bag distension. The entire volume of gas captured within thisbag was then made available for the next inhalation. Such systemsincreased the duration of the breathable gas supplied; however, inactuality, the dead volume is not a constant value nor is it a constantratio with respect to inspiratory tidal volume. Accordingly, dependingupon the fixed volume chosen, the apparatus can be less than efficientor in some instances, can be quite hazardous due to excess amounts of COrebreathed.

SUMMARY OF THE INVENTION The present invention retains optimumefficiency and safety regardless of high or low work rates by variablycontrolling the volume of exhaled breath which is saved, in accordancewith the users breathing.

A sensing means senses the tidal volume and the flow rate of aninspiration, and on the subsequent expiration the sensing meanseffectively causes a volume limiting device to proportionately limit theamount of exhaled breath flowing into a gas collector. The gas thuscollected is available to supplement the next inhalation.

The gas collector may, if desired, be formed of two sections, a firstsection having a fixed maximum volume and a second section having avariable maximum volume.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a curve illustrating thevariation in CO, concentration as a function of expired volume;

FIG. 2 is a curve illustrating the dead volume as a function of inspiredtidal volume;

FIGs. 3A and 3B illustrate, in block diagram form, two embodiments ofthe present invention;

FIG. 4 illustrates in more detail another embodiment of the presentinvention;

FIG. 5 is a curve illustrating inhalation and exhalation as a functionof time;

FIG. 6 illustrates a variation of the embodiment of FIG. 4;

FIG. 7 is a front view of a fire fighter utilizing the apparatus of FIG.6;

FIG. 8 is a side view of FIG. 7, with portions broken away; and

FIG. 9 is a block diagram of another embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a typical plot ofinstantaneous CO; content as a function of a volume of expired breathand serves to define certain terms. The vertical axis represents COconcentration in the expired breath and the horizontal axis representsthe expired volume. The initial expiration contains no CO, whatsoever,and thereafter, the CO content rises. At inflection point A, theinstantaneous CO concentration is somewhat less than 2.5%; however, thecumulative CO content up to this point is less than 1%. This volume isapproximately equal to the volume of the bronchial tree and upperrespiratory passages not subject to gas exchange. This volume is termedthe anatomic dead volume and is designated on the horizontal axis by theterm AV Respiratory gas exchange takes place in the alveoli of the lungsand point B on the curve represents instantaneous CO concentrationstypical of alveolar gas and is in the order of 44.5%. The cumulative COcontent up to point B, however, would only be about 2-2.5% and within anacceptable range for rebreathing. The volume corresponding to point B isdesignated the kinetic dead volume KV and may be defined as the amountof exhaled gas needed to flush the dead space gas from the respiratorypassages up to the appearance of'pure alveolar gas. The kinetic deadvolume is approximately equal to twice the anatomic dead volume.

Proceeding along the curve, point C is reached and represents the tidalvolume, that tis, the volume of gas expired during the respiratorycycle, and is designated V- As total lung volume increases due toincreased depth of inspiration, so also does the dead volume increase. Atypical relationship is illustrated in FIG. 2 wherein the vertical axisrepresents the kinetic dead volume in milliliters and the horizontalaxis represents the inspired tidal volume in liters. The sloped straightline curve of FIG. 2 intersects the vertical axis at 300 milliliters andhas a slope of approximately 7.5 milliliters increase in kinetic deadvolume per milliliter increase in tidal volume. The actual slope of thestraight line varies somewhat, according to different investigators inthe field of respiratory physiology and according to recent data, FIG. 2represents a somewhat conservative viewpoint. That is, the curve in FIG.2 is less steep than that predicted by some investigators. In addition,the typical curve is based on an attest anatomic dead volume ofmilliliters (the kinetic dead volume is approximately tiwce that or 300milliliters) corresponding approximately to a user's body weight of I50lbs. The base value varies per individual roughly on a direct milliliterof anatomic dead volume per pound of body weight basis.

Various prior art devices utilize a fixed maximum volume breath-savingarrangement. Let it be assumed for purposes of comparison, that thebreath-saving volume is designed to hold a maximum capacity of 400milliliters of exhaled breath; this is a represented by the horizontalline in FIG. 2 labeled Prior Art If the user is working at a rate suchthat his inspired tidal volume is a little more than 1.8 liters, thenfrom the kinetic dead volume curve it is seen that there is 400milliliters of dead volume containing gas which can be rebreathed and,accordingly, the apparatus is efficient for that particular work rate.

Consider now a situation where the user is at rest. In such instance,his kinetic dead volume is only 300 milliliters, but he is stillcollecting 400 milliliters of exhaled gas; and thus an unsafe andpotentially dangerous condition exists whereby the user will berebreathing saved gas having a C content above an established safemaximum. Consider now the other extreme, where the user is doing heavywork such that his inspired tidal volume is around 2.5 liters. In thatinstance, his kinetic dead volume will be in the order of 450milliliters, yet his apparatus is sized to only collect 400 milliliters,representing a less than efficient operation. To eliminate any potentialhazard, the fixed maximum volume may be reduced to, for example, 300milliliters; however, the apparatus will always be less than efficientfor all situations except when the user is at rest.

The apparatus of the present invention is constructed and arranged suchthat an amount of exhaled gas is collected which closely approximatesthe kinetic dead volume curve, ideally to track right on it, orpractically, to operate in a zone right below it. Thus, when the user isat rest an exhaled volume close to 300 milliliters will be captured, andthis volume will increase as the work rate and, accordingly, theinspired tidal volume increases to retain the optimum combination ofefficiency and safety regardless of high or low work rates.

One way of accomplishing this variable volume collection of exhaled gasis illustrated in FIG. 3A in block diagram form. A source of breathinggas provides oxygen-containing gas to the user via passageway 12, ondemand, and at the ambient pressure. Exhaled gas from the user passes toa gas collector means 16 which may be a flexible bellows arrangement andmay, if desired, be constructed in two sections a first section 16ahaving a fixed maximum volume and a second section 16b having a variablemaximum volume and which closes as determined by a volume limitingdevice 17. The section 16a may have a volumetric capacity equivalent tothe at-rest dead volume of the user and the volumetric capacity ofsection 16b may be such as to accommodate the expected remainder of thekinetic dead volume.

The volume limiting device 17 operates in response to a sensor means 18disposed relative to passageway 12 to sense the flow rate and volume ofan inspired breath to close the volume limiting device at the propertime.

Inhaled gas in FIG. 3A is designated by the solid line arrows andexhaled gas by the dotted line arrows. After the volume limiting devicehas closed the gas collector 16 in response to a signal from the sensor18, further exhaled gas is discharged to the ambient medium through arelief valve 20.

For some operations, it may be desired to maintain the breathing gasfrom the source in a dry condition so as to be useful for defoggingpurposes. By way of example, FIG. 35 illustrates an arrangement foraccomplishing this with the provision of two separate passageways, theinhalation passageway 26 and exhalation passageway 27. A source ofbreathing gas 28 provides the oxygen-containing gas to the user who alsobreathes previously collected gas from the gas collector 30 which may,as previously discussed, be comprised of a first secion 30a having afixed maximum volume and a second section 30b having a variable maximumvolume. Sensors 32 and 33 sense the flow rate and volume of inhaledgases in respective passageways 26 and 27 to open the volume limitingdevice 35 to enable section 30b to capture exhaled gas over and abovethat captured by section 30a. The remainder of the exhaled gas isdischarged to the ambient medium by way of relief valve 36.

For the fluidic embodiments of the invention, an indication of theinspired tidal volume can be obtained by a measurement of theinspiration flow rate over the inhalation period. For very slowbreathing or in instances where the user may hold his breath, there isthe possibility of alveolar and dead volume gases mixing within therespiratory passages, and the exhaled breath would not be CO free.Accordingly, it is preferable that means be provided to initiate closingoff of the variable volume gas collector, should this type of breathingoccur. That is, the amount of exhaled gas captured decreases as afunction of the time from inhalation to exhalation.

Yet another arrangement for varying the amount of collected exhaledbreath in accordance with the users breathing is illustrated in moredetail in FIG. 4. The arrangement utilizes a face or head cover 40closed to the ambient environment when worn by the user in conjunctionwith an oralnasal mask 42 which fits over the nose and mouth of the userand closely conforms to the facial contours. The oral-nasal mask 42 andhead cover 40 may be integrated into one unit; however, they are shownseparated in FIG. 4 and connected by a valved passageway 44, for ease ofexplanation.

Breathing gas is supplied on demand on the head cover 40 by means ofinhalation demand valve 46 and then through a venturi passgeway 48.

The gas collector 50 combines into one unit the previously discussedfixed and variable maximum volumes and includes an outer wall portion 51and an internal cylindrical collapsible bellows 53 normally urged to itsextended position by means of spring 54.

Means for limiting the downward stroke of the bellows 53 is provided andtakes the form of a sensor actuator 58 also in the form of a cylindricalcollapsible bellows which intercepts and halts the movement of thebellows 53. The sensor actuator 58 is communicative with passageway 60through aperture 61 as long as moveable button 63 is held away from theaperture by spring 64.

Means for sensing the parameters of an inhalation are provided in theform of sensor 67 divided into three chambers 69, 70 and 71 by means ofmovable diaphragms 73 and 74 connected together by means of rods 75.Spring 78 normally urges the plate 80 of diaphragm 73 against theopening of passageway 60, and passageway 60 is communicative withchamber 71 through a restricted passage sensor orifice 82.

Chamber 69 is communicative with the oral-nasal mask 42 by way ofpassageway chamber 70 is communicative with the head cover 40 by meansof passageway 86; and chamber 71 is connected to the throat 88 ofventuri 48 by means of passageway 89. In addition to communication withthe head cover 40 and sensor 67, the oral-nasal mask is communicativewith the users mouth as indicated by the double-ended arrow, iscommunicative with the gas collector 50 through valved passageways 92and 93, and is additionally communicative with the ambient mediumthrough relief valve 95. The operation of the apparatus of FIG. 4 willnow be explained with additional reference to FIG. 5 illustrating, by anidealized curve, a single inhalation and exhalation as a function oftime. Flow, in terms of liters per minute, is plotted on the verticalaxis.

At time the user begins to inhale, through springloaded one-way valve100, gas saved in the collector 50 from a previous exhalation. Thissaved gas is confined to the space between the bellows 53 and wall 51and is shown stippled. As the user continues to inhale the previouslyexhaled gas, the pressure within the collector 50 continues to decreaseand the bellows 53 moves to its extended position. At t, the bellows 53will have moved to a position such that disc 102 on top of the bellows53 contacts the tilt lever 104. in so moving, the tilt lever 104 pivotedaround point 105 depresses valve disc 107 against the action of spring108 which was forcing it against the valve seat 110. With the demandvalve 46 thus opened, breathing gas at a pressure P, is supplied to theuser through venturi 48, head cover 40, passageway 44, and spring-loadedone way valve 112.

A flow straightener, such as a honeycomb section or screen 115, isprovided just prior to the converging portion of the venturi in order toprovide a more uniform flow. Due to the venturi action, the gas flowcauses a pressure reduction at the venturi throat 88 and this pressureP, is low compared to the pressures in the head cover 40 and oralnasalmask 42; this pressure P, is also the pressure in chamber 71 of sensor67 by virtue of the passageway 89. Similarly, by virtue of pas sageway86, the pressure P, in chamber 70 is the same as the pressure in headcover 40 and the pressure P;, of chamber 69 is the same as the pressurein the oral-nasal mask 42 by virtue of the communication 85. At thistime, pressure P, is lower than pressure P, or F and, consequently, themovable diaphragms 73 and 74 are forced to a position such that thediaphragm plate 80 closes off the opening of passageway 60.

The pressure within the sensor actuator 58 is P, and, by means ofpassageway 60, this is the same pressure that appears at the left-handside of sensor orifice 82. From time t, to t, as the user inhales, thepressure drop P,-P, across the sensor orifice 82 results in a flow rateof gas from the sensor actuator 58 being about proportional to the flowrate through the venturi. Since the flow rates occur over the sameperiod of time, the volume change in the sensor actuator 58 is aboutproportional to the volume inhaled by the user; and so, at the end ofinhalation, the sensor actuator 58 is in a somewhat collapsed positionindicative of the inhaled volume. Exhalation commences at time t,, andthe exhaled breath starts to fill the collector 50 through springloadedone way valve 120. Exhalation continues into the collector from time t,to t at which point the downward stroke of bellows 53 will be stopped byvirtue of disc 102 engaging button 63 to force it against the aperture61. Thus no more gas can be accepted by the collector 50 and thepressure in the oral-nasal mask 42 rises slightly, causing the remainderof the exhalation to be discharged to the ambient medium through therelief valve 95.

The construction and operation of the sensor actuator is such that, ifthe wearer holds his breath after inhaling, the volume of the sensoractuator 58 and its position will slowly increase because gas willslowly flow through the sensor orifice 82 from the slightly higherpressure P, in the head cover relative to the pressure P, in the sensoractuator. (Since there is no flow through the venturi, the pressure P,will be equal to the pressure P The amount of total possible accumulatorvolume,

accordingly, will become smaller as the wearer holds his breath and thisis desirable because the longer the breath is held, the more time thereis for CO, rich gas to mix with the CO, free gas in the pulmonarypassages and less gas should be accumulated for rebreathing in suchinstance.

At time corresponding to t in the cycle, the user begins to inhale thepreviously collected gas from the collector through valve 100. Thisresults in a slight pressure drop in the oral-nasal mask 42. With Pslightly less than the pressure P: in the head cover 40 (and with P,equal to P the movable diaphragms 73 and 74 will move against the actionof spring 78 to thereby allow discharge into the sensor actuator 58 fromchamber by way of passageway 60 thereby resetting the sensor actuator toits maximum length position for the next inhalation.

If desired, a manual override may be provided to supply the user withgas and this may be accomplished by the provision of a purge lever 123which, when pushed up, will open the demand valve 46.

In order to insure a clear passageway through sensor orifice 82, screens125 on either side of the orifice are provided to prevent blockagethereof. With respect to the various spring-loaded valves illustrated,the spring force relationship is such that, of the two valves conductinggas out of the oral-nasal mask 42, valve 120 will open before valve andwith respect to the two valves conducting gas into the oral-nasal mask42, valve will open before valve 112.

With respect to the idealized curve of FIG. 5, it is to be noted thatflow rate vs. time is plotted. The area under the curve therefore, isequal to the volume of gas inhaled (n, to or exhaled (I, to 1,).

The embodiment of the invention illustrated in FIG. 4 is of the typewherein gas is supplied to the user in sequence, that is, first from thegas saver (t to r.) and then from the supply (t, to Flow rate is sensed(and accordingly, volume) only from t, to 1,.

Other arrangements contemplate the simultaneous provision to the user,of saved and supply gas, so that measurement is made of total inhaledgas (e.g. t to t to control the amount of gas saved on exhalation. Additionally the volume limiting device can also be actuated in response tonot only inhaled gas but to exhaled gas, the inhalation flow rategoverning the opening of communication to the gas saver and theexhalation governing the closing of such communication.

The apparatus herein may be utilized in various fields, such as diving,space or rescue work. For example, the apparatus of FIG. 4 is shown insimilar form in FIG. 6 as might be used by a fire fighter as illustratedin FIGS. 7 and 8. The components of FIG. 6 are identical to thosedescribed in FIG. 4 and have been given like reference numerals. Oneexception is the gas collector 50, which has now been divided into afirst section 50a having a fixed maximum volume and a second section 50bhaving a variable maximum volume. The operation of FIG. 6 is the same asthat described in FIG. 4 in that, after the user inhales the previouslyexhaled gas from collector 50, bellows 53a will actuate the tilt leverto cause supply gas to flow. The pressure drop P P causes a reduction inthe volume of sensor actuator 58 in proportion to the inhaled volume. Bymaking the spring force of spring 54a less than that of spring 54b, asthe user exhales into the collector 50, bellows 53a will be collapsedfirst, after which bellows 53b will collapse to a position determined bythe sensor actuator 58, as previously described. The volumes may besized such that the first section and associated passageways isapproximately equal to the at-rest dead volume while the volume of thesecond section 50b and its associated passageways is equal to theremaining maximum expected dead volume. In order to accommodate a widevariety of users, the apparatus can be designed with gas collectorvolumes in, for example, a small, me dium and large range.Alternatively, a minimum expected user weight may be determined and theapparatus tailored to that weight, thus adapting to a broad range ofindividual users and having nearly universal application.

Some components illustrated in FIGS. 7 and 8 have been described withrespect to FIGS. 4, 6, and accord ingly, have been given like referencenumerals. The gas collector sections 500 and 50b are seen on the firefighters mask and section 500 has a protective screen 128 and the valveactuator 58 is supported within sec tion 50b by means of a spider 130.

Above the relief valve 95, there is positioned a voice disc I33, wherebythe fire fighter may communicate with other personnel.

Demand valve 46 is seen with purge lever 123 and venturi 48, and a gassupplying hose 136 is shown in FIG. 8 as being connected to a source ofbreathing gas, tank 139, by means of a quick-disconnect 141 and a firststage regulator 143.

Many variations of the breathing apparatus are possible depending uponthe specific design of components. The flow/volume sensor and the volumelimiting devices could be mechanical, electromechanical orfluidmechanical. The sensor means could be in the form of pressuretransducers sensing pressure difference variations to thereby activate asolenoid flow limiting valve to vary the captured exhaled volume.

Whereas the embodiments thus far described operate with a previoushistory of the user's breathing, the embodiment illustrated in blockdiagram form in FIG. 9 operates on a breath-by-breath examination of theexhaled gas. Operation is accomplished by the provision of a sensor I47operable to provide an output signal indicative of the instantaneous COcontent of the exhaled breath. The output signal from sensor I47 isreceived by electronic circuit 149 to activate a valve 151 to a closedposition, thus shutting off exhaled gas flow to gas collector [52.Operation can be such that the valve will be shut off when the output ofsensor 147 indicates that alveolar gas is present, or alternatively, theoutput of sensor 147 can be integrated such that the electronic circuit149 will shut the valve 151 when a total accumulated CO, content reachesa predetermined, dangerous level.

We claim:

1. Breathing apparatus comprising:

a. means for providing a user with a gas to be breathed;

b. a gas saver means for the capture of the user's exhaled breath;

c. sensing means for sensing an indication of the volume of aninhalation by the user; and

d. means responsive to said sensing means for closing off said gas savermeans, as a function of said inhalation so that no more exhaled gas willbe accepted thereby during the exhalation.

2. An apparatus according to claim 1 which includes:

a. means for decreasing the amount of exhaled gas captured as a functionof the time from inhalation to exhalation.

3. Breathing apparatus comprising:

a. means for providing a user with the gas to be breathed;

b. a gas saver means for the capture of the users exhaled breath andhaving a variably volumetric capacity defined by a moveable portion;

c. sensing means for establishing a flow rate of gas proportional to theflow rate of an inhalation by the user;

d. a moveable actuator means connected to said sensing means andmoveable in proportion to said flow rate of gas;

e. said moveable actuator means being positioned relative to said gassaver means for limiting the capture capacity of said gas saver means todefine a maximum volumetric capacity for the subsequent exhalation.

4. Apparatus according to claim 3 wherein:

a. said moveable actuator means is positioned to intercept and halt themovement of said moveable portion of said gas saver means.

5. Apparatus according to claim 4 wherein:

a. said gas saver means is defined by two separate sections, the firstsection having a fixed maximum volumetric capacity and the secondsection having a variable maximum volumetric capacity.

6. Apparatus according to claim 4 wherein:

a. said gas saver means includes a rigid outer wall portion and aflexible inner portion, the volume between them being for reception ofexhaled breath;

b. said moveable actuator means is a collapsible bellows positionedwithin said flexible inner portion of said gas saver means.

7. Apparatus according to claim 6 wherein:

a. the interior of said bellows is communicative with said sensing meansso that gas flow may be established between them;

b. the volume of said bellows being decreased as the user inhales, inproportion to the inhalation.

8. Apparatus according to claim 7 which includes:

a. means for resetting said bellows to an initial posi tion prior to thenext inhalation.

9. Apparatus according to claim 3 which includes:

a. an inlet for the supply of said gas to be breathed;

b. a venturi section connected to said inlet;

c. said sensing means including an orifice;

(I. one side of said orifice being communicative with the throat of saidventuri section;

e. the other side of said orifice being communicative with said moveableactuator means.

10. Breathing apparatus comprising:

a. a face cover closed to the ambient environment when worn by a user;

b. an oral-nasal mask in valved communication with said face cover;

c. a gas inlet for supplying breathing gas to said face cover;

d. a venturi section having an input portion connected to said gas inletand an output portion connected to said face cover;

e. a gas saver means in valved communication with said oral-nasal maskfor capturing a portion of the users exhaled breath and supplying it tothe user on the subsequent inhalation;

f. a moveable actuator means positioned with respect to said gas saverfor limiting the volume of gas captured by said gas saver means;

g. sensor means connected between said moveable actuator means and thethroat of said venturi section for establishing a flow rate of gasproportional to the users inhalation, to proportionally move saidmoveable actuator means.

11. Apparatus according to claim 10 wherein:

a. said gas saver means includes means for opening said gas inlet afterinhalation by the user of the previously saved exhaled gas.

12. Apparatus according to claim 10 wherein:

a. said moveable actuator means is a gas containing moveable bellows;

b. said sensor means includes a plurality of chambers, 21 first chamberbeing communicative with said throat of said venturi, a second chamberbeing communicative with said face cover and a third chamber beingcommunicative with said oral-nasal mask;

c. a plurality of moveable diaphragm members separating said chambersfrom one another;

d. a passageway communicating the interior of said bellows with saidsecond chamber, one of said dia' phragm members normally closing saidpassageway;

e. an orifice connected between said passageway and said first chamberwhereby when said passageway is closed by said diaphragm member and theuser inhales, gas will flow from the interior of said bellows, throughsaid passageway, through said orifice, into said first chamber andventuri section;

f. said passageway being open to said second chamber when the pressurein said second chamber is greater, by a predetermined amount, than thepressure in said third chamber, to allow gas flow back into the interiorof said bellows to reset said moveable actuator means to an initialposition,

13. Apparatus according to claim 10 wherein:

a. said gas saver means is in two sections, a first section having afixed maximum volumetric capacity, the second section having a variablemaximum volumetric capacity;

b. said first and second sections being carried by said face cover.

1. Breathing apparatus comprising: a. means for providing a user with agas to be breathed; b. a gas saver means for the capture of the user''sexhaled breath; c. sensing means for sensing an indication of the volumeof an inhalation by the user; and d. means responsive to said sensingmeans for closing off said gas saver means, as a function of saidinhalation so that no more exhaled gas will be accepted thereby duringthe exhalation.
 2. An apparatus according to claim 1 which includes: a.means for decreasing the amount of exhaled gas captured as a function ofthe time from inhalation to exhalation.
 3. Breathing apparatuscomprising: a. means for providing a user with the gas to be breathed;b. a gas saver means for the capture of the user''s exhaled breath andhaving a variably volumetric capacity defined by a moveable portion; c.sensing means for establishing a flow rate of gas proportional to theflow rate of an inhalation by the user; d. a moveable actuator meansconnected to said sensing means and moveable in proportion to said flowrate of gas; e. said moveable actuator means being positioned relativeto said gas saver means for limiting the capture capacity of said gassaver means to define a maximum volumetric capacity for the subsequentexhalation.
 4. Apparatus according to claim 3 wherein: a. said moveableactuator means is positioned to intercept and halt the movement of saidmoveable portion of said gas saver means.
 5. Apparatus according toclaim 4 wherein: a. said gas saver means is defined by two separatesections, the first section having a fixed maximum volumetric capacityand the second section having a variable maximum volumetric capacity. 6.Apparatus according to claim 4 wherein: a. said gas saver means includesa rigid outer wall portion and a flexible inner portion, the volumebetween them being for reception of exhaled breath; b. said moveableactuator means is a collapsible bellows positioned within said flexibleinner portion of said gas saver means.
 7. Apparatus according to claim 6wherein: a. the interior of said bellows is communicative with saidsensing means so that gas flow may be established between them; b. thevolume of said bellows being decreased as the user inhales, inproportion to the inhalation.
 8. Apparatus according to claim 7 whichincludes: a. means for resetting said bellows to an initial positionprior to the next inhalation.
 9. AppaRatus according to claim 3 whichincludes: a. an inlet for the supply of said gas to be breathed; b. aventuri section connected to said inlet; c. said sensing means includingan orifice; d. one side of said orifice being communicative with thethroat of said venturi section; e. the other side of said orifice beingcommunicative with said moveable actuator means.
 10. Breathing apparatuscomprising: a. a face cover closed to the ambient environment when wornby a user; b. an oral-nasal mask in valved communication with said facecover; c. a gas inlet for supplying breathing gas to said face cover; d.a venturi section having an input portion connected to said gas inletand an output portion connected to said face cover; e. a gas saver meansin valved communication with said oral-nasal mask for capturing aportion of the user''s exhaled breath and supplying it to the user onthe subsequent inhalation; f. a moveable actuator means positioned withrespect to said gas saver for limiting the volume of gas captured bysaid gas saver means; g. sensor means connected between said moveableactuator means and the throat of said venturi section for establishing aflow rate of gas proportional to the user''s inhalation, toproportionally move said moveable actuator means.
 11. Apparatusaccording to claim 10 wherein: a. said gas saver means includes meansfor opening said gas inlet after inhalation by the user of thepreviously saved exhaled gas.
 12. Apparatus according to claim 10wherein: a. said moveable actuator means is a gas containing moveablebellows; b. said sensor means includes a plurality of chambers, a firstchamber being communicative with said throat of said venturi, a secondchamber being communicative with said face cover and a third chamberbeing communicative with said oral-nasal mask; c. a plurality ofmoveable diaphragm members separating said chambers from one another; d.a passageway communicating the interior of said bellows with said secondchamber, one of said diaphragm members normally closing said passageway;e. an orifice connected between said passageway and said first chamberwhereby when said passageway is closed by said diaphragm member and theuser inhales, gas will flow from the interior of said bellows, throughsaid passageway, through said orifice, into said first chamber andventuri section; f. said passageway being open to said second chamberwhen the pressure in said second chamber is greater, by a predeterminedamount, than the pressure in said third chamber, to allow gas flow backinto the interior of said bellows to reset said moveable actuator meansto an initial position.
 13. Apparatus according to claim 10 wherein: a.said gas saver means is in two sections, a first section having a fixedmaximum volumetric capacity, the second section having a variablemaximum volumetric capacity; b. said first and second sections beingcarried by said face cover.